Electrolytic device



March 31, 1942. J. B. BRENNAN 2,277,687

ELECTROLYT IC DEVICE Filed May 24, 1959 INVENTOR.

ATTGRNEYS Patented Mari 3l, 1942 UNITED STATES PATENT OFFICE ELECTROLYTIC DEVICE Joseph B. Brennan, Euclid, Ohio Application May 24, 1939, Serial No. 275,481

4 Claims.

This invention relates to electrolytic devices such as electrolytic condensers, rectiiiers and the like, and particularly to electrolytic devices wherein one or more of the electrodes is composed of a lm forming metal provided with an electro-formed dielectric film. The invention will be described herein with particular reference to electrolytic condensers but it is to be understood that the invention may be applied to other types of elcctrolytic devices.

In electrolytic condensers of the type embodying one or more filmed electrodes the capacity depends upon, among otherthings. the area of the metal exposed to the action of the electrolyte. During the film forming operation a dielectric film is formed on the metal which is coextensive with the surface thereof and conforms to the irregularities of the surface. Thus an increase in surface area. will result in an increase of the area of the dielectric film and a corresponding increase in the"capacity of the condenser. Further, an increase in the area of an unfilmed electrode, such as the cathode of a condenser intended for direct current service, improves the efiiciency and durability of the electrode, as pointed out in my Patent No. 2,154,026. It is therefore among the objects of this invention to produce an economical and efficient electrode for electrolytic devices wherein the effective surface area of the electrode is very large in proportion to the weight or mass of material employed, whereby, in the case of a filmed electrode or anode, an extremely high capacity can be obtained with the use of only a small amount of film forming metal, and, in the case of an electrode constituting the cathode of a condenser or similar device, the efficiency and durability of the device will be enhanced. Another objeot of my invention is to provide a compact electrolytic device having an extremely high capacity. Another object is to provide an efiicient and durable electrolytic condenser or similar device. A further object is to provide an electrolytic device which can be manufactured at low cost. Another object is to provide an efficient and economical method of making such electrolytic devices. A

Further objects and advantages of my invention will be apparent from the following description of preferred forms thereof, reference being made to the accompanying drawings wherein preferred forms of my invention are illustrated somewhat diagammatically. In the drawing, Figure 1 is a vertical sectional view through a wet type condenser made according to my invention; Figure 2 is a transverse section taken along the line 2--2 of Figure 1; Figure 3 is a sectional view showing my invention as applied to a condenser of the dry or paste type; Figure 4 is a plan view of one of the electrodes of the condenser shown in Figure 3; and Figure 5 is a section through the electrode illustrated in Figure 4 as indicated by the line 5-5 on Figure 4.

Briefly, my invention contemplates an electrolytic device, such as an electrolytic condenser, embodying one or more electrodes made up of accumulations or masses of ne metallic filaments, strands, or fibers, preferably intertwined, felted or matted together in the form of a metallic wool. In such form a small weight of .metal has a very extended surface area exposed to the action of the electrolyte when the material is incorporated in a condenser. The material is porous and permeable with the result that the electrolyte can penetrate substantially throughout an electrode madeof a metallic wool and thus all of the metal can be elciently utilized. As the filaments in the metallic wool may be made of considerable length and matted together, the resistance of the material is low and the resistance of the electrode is preferably further reduced by incorporating conductive paths throughout the electrode. The filaments composing the wool may be of any convenient form and may be produced for example by cutting long, fine chips or shavings from a metallic bar or wire. Preferably the filaments are of irregular cross-section, or at least are not round, so that each filament will have a greater area per unit of mass than would be the case if the filaments were of round cross-section. The filaments may be of varying cross-sectional area depending upon the requirements of the service, the smaller the filament employed the greater the effective area that will be obtained but with larger filaments the resistance of the electrodes will be less. Preferably, the minimum cross-sectional dimension of the filaments is not greater than 0.005 inch.

Filmed electrodes or anodes may be composed of aluminum filaments or fibers, or of filaments or bers of other film-forming metals such as magnesium, or various alloys. Unfilmed electrodes such as cathodes for direct current condensers may be composed of a film forming metal, or of a non-filming metal which will not contaminate the electrolyte-copper, for example.

The metallic wool may if desired be subjected to treatment to further increase the effective area thereof. For example, the area may be further lncreased by subjecting the material to an etching process such as' that described in my prior Patent No. 2,154,027. It 'desired fine partion the filaments so that the'filaments are bound together somewhat and the effective area of film forming metal is greatly increased. lIf desired the metallic wool may be subjected to pressure so as to make it more compact and homogeneous and so as to form the electrodes into desired definite shapes. The necessary terminals or conductors may be connected to the electrodes for example by Spraying thereto, by welding or riveting, or merely by forcing a wire into the mass of the metallic wool.

Referring to the drawing, in Figures 1 and 2 I have illustrated one type of electrode as adapted for use with electrolytic condensers of the wet type. Such a condenser may comprise a container I! for the electrolyte, which also functions as the cathode of the condenser and is provided with a closure Il, a downwardly extending neck portion I2 for mounting the condenser in an apertured support and through which the terminal Il extends, the terminal passing through a rubber gromet i which may be compressed into fluid tight engagement with the neck and the terminal by deforming the neck portion as indicated at I6. Within the container I may provide a spacer I1 which functions to prevent contact between the anode Il, and the container or cathode and the container is filled with a suitable film maintaining electrolyte such as a solution of borax and boric acid.

The electrode or anode Il comprises, in this form of my invention, a mass of fine filaments or fibers of aluminum or other suitable film forming metal matted together and subjected to suflicient pressure to form them into substantially cylindrical shape as shown. The electrode may be supported within the container by the upper portion of the terminal wire or rod I4 which is formed into a helical shape as indicated at I! and screwed into the mass of filaments in the manner of a corkscrew. By such an arrangement effective contact is made between the terminal Il and the electrode proper, and further. the riser extending throughout the elec* trode functions to reduce the resistance of the electrode and results in the effective utilization of all of the material of which the electrode is composed.

The electrode thus consists of a porous mass of filaments of film forming material and the electrolyte can permeate throughout the mass. The extensive surfaces of the filaments or strands may be provided with dielectric films in any desired manner, for example by subjecting the electrode to electrolysis as an anode in a manner known to those skilled in the art in a suitable film forming electrolyte such as a solution of borax and boric acid. The film forming operation is continued until the leakage current is reduced to thc desired low value at the maximum forming voltage, the forming voltage ordinarily being somewhat in excess ol the voltage at which the condenser is designed to operate in service. Alter the forming operation is completed the electrode may be mounted in the condenser as shown. the condenser being completed by filling the container with electrolyte to the desired level and applying the closure member ii.

In Figures 3, 4, and 5 I have illustrated one form oi my electrode as applied to a condenser oi the dry or paste type. This type of condenser cles of mm forming molten metal may be sprayed terminal 3i.

operation as indicated at 4i to reduce the resistance of the electrodes and increase their mechanical strength. The terminals may be welded to the compacted edge portions of the electrodes as indicated at I2.

If such a condenser is intended for alternating current service all of the electrode plates will be composed of mats of film forming material and all of the mats will be provided with dielectric films. If the condensers are intended for direct current service only one of the anodes need bc provided with dielectric films. For example, the electrodes 21 and 29 in the embodiment shown may be of aluminum and formed of dielectric films, while in a direct current condenser the re maining electrodes or cathodes 26 and 28 may be of non-filming material such as copper or, if composed of aluminum filaments, the surfaces of the filaments would not be provided with films.

The electrodes after assembly as shown may be impregnated with a suitable viscous or pasty electrolyte such as the urea formaldehyde electrolyte described and claimed in my prior Patent No. 2,095,966. Obviously other suitable electrolytes may be employed and as those skilled in the art will appreciate other film forming materials or alloys may be used and the electrodes can be adapted to various other well known types of condensers such as the conventional rolled condensers.

While I prefer to employ cathodes composed of metallic wool as shown, particularly in conjunction with condensers of the dry or paste type, it is evident that other types of cathodes, such as pieces of foil, may be employed with anodes made according to the present invention. Similarly, cathodes made according to the present invention may be used with anodes of various types.

In condensers made according to my invention the extremely large effective area per unit of mass of the electrodes makes it possible to Droduce condensers having small volume and incorporating only a small weight or mass of film forming material yet having relatively large capacities. Thus my condenser may be manufactured with little cost for material and, as the manufacturing operations themselves are simple, it is possible to produce high capacity condensers at low cost. The electrodes have low specific resistance and thus the condensers are elcient and operate with low power factor losses. Electrodes made according to my invention and utilized as cathodes in electrolytic condensershave large surface areas in contact with the electrolyte, thus keeping the cathode current densities at low values and increasing the efficiency and lengthening the life of the condensers.

Various changes and modifications in my invention will be apparent to those skilled in the art. It is therefore to be understood that my patent is not limited by the foregoing description of preferred forms of my invention or in any manner other than the appended claims, when given the range of equivalents to which my patent may be entitled.

I claim:

1. In an electrolytic condenser of the type embodying a. film-maintaining electrolyte and a container therefor which also constitutes the cathode of the condenser, an anode immersed in said electrolyte within said container and comprising a mass of metallic wool composedvof film-forming metal, and having a wire composed of lmforming metal extending into said mass. said wire supporting said anode within said container.

2. In an electrolytic condenser of the type embodying a film-maintaining electrolyte and a container therefor which also constitutes the cathode of the condenser, an anode immersed in said electrolyte within said container and comprising a mass of attenuated filamentspof filmforming metal, and terminal means for supporting said anode comprising a riser composed of film-forming metal having a portion thereof formed into a helix and threaded into,y said mass of filaments, said riser being supported by said container and insulated therefrom and having another portion thereof extending to the exterior of said container.

3. An electrode for an electrolytic device of the type embodying a hlm-maintaining electrolyte comprising a mass of metallic wool having finely divided metallic particles sprayed thereon.

4. In an electrolytic device, an electrode comprising a mass of metallic wool, and means for connecting said electrode to an external circuit comprising a metallic member formed into a helix and extending into said mass of metallic wool.

JOSEPH B. BRENNAN. 

